1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a high-definition screen.
2. Description of the Related Art
A liquid crystal display device as a kind of display device includes: a TFT substrate where pixels including pixel electrodes, thin film transistors (TFTs) and the like are arranged in a matrix form; a counter substrate opposed to the TFT substrate; and liquid crystal sandwiched between the TFT substrate and the counter substrate. The display device forms an image by controlling transmittance of light through the liquid crystal molecules on a per-pixel basis.
The liquid crystal display device requires backlight because the liquid crystal per se does not emit light. Because of the increasing usage pattern as a portable device, the liquid crystal display devices of medium/small sizes are faced with the need for reduction of power consumption. In the pursuit of the reduction of power consumption through more efficient use of light from the backlight, Japanese Unexamined Patent Application Publication No. 2011-227191 discloses a structure where the TFT substrate is formed with a reflection layer at a region except for a light transmission region such that the power consumption of the backlight is reduced by reutilizing the light from this reflection layer (Japanese Unexamined Patent Application Publication No. 2011-227191).
The medium/small sized liquid crystal display devices have a high-definition screen. As the liquid crystal display device has the higher definition, a liquid crystal display panel has the lower aperture ratio. Therefore, the use efficiency of light from the backlight decreases with the increase in the screen resolution. In other words, the display device is increased in the power consumption of the backlight to keep the same brightness as before.
The technique disclosed in the cited literature 1 suggests the structure where the reflection film such as of metal is applied to the overall TFT substrate except for the apertures so as to reutilize the light from the backlight. However, this structure adversely affects signal writing speed and the like because a substantial capacitance is formed between the reflection film and image signal lines or scanning lines.